Magnetically-operated device



H. D. JAMES 1.719.115

MAGNETICALLY OPERATED'DEVIGE Filed NOV. '7, 1927 July 2, 1929. i

ATT'ORNEY ParentedfJuly 2, 1929. i'

UNITED sTATEs PATENT OFFICE.

HENRY D. JAMES, 0F EDGEWOOD, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION 0F PENNSYLVANIA.

MAGNETICALLY-OPERATED DEVICE.

Application filed November 7, 1927. Serial-No. 231,533.

My invention relates generally to electromagnetically operated devices suitable for alternating-current systems, and particularly to means for retarding the action of such devices.

The object of my invention is lto provide for controlling the action of an electromagnetically operated device by a thermallyresponsive latch.

Another object of my invention is to provide for utilizing an electric current for heating-a thermally-responsive latch and for interrupting the heating process, without opening the heating circuit, when the latch is sprung.

A further object of my invention is to provide for utilizing thermally-responsive de. vices having a delayed action for controlling the operation .of the accelerating switches of a motor-control system.

For a complete understanding of the invention and the operation of its parts, reference may be had to the following description which should be read in conjunction with the accompanying drawing, in which:

Figure 1 is a side elevational View of a magnetically operated device constructed in accordance with the invention.

Fig. 2 is a top plan View of a thermally responsive latch.

Fig. 3 is a diagrammatic view of a system of control foran induction motor, showing an electromagnetically operated device constructed in accordance with the invention and connected in the control system.

n Referring now to Figs. 1 and 2, a core 11 of an electromagnetically operated device is constructed `in a substantially U-shapc. A lever 12 having a tail piece 13 is pivotally mounted on one of the legs of the core 11. The lever 12`eXten'ds in a substantially horizontal plane,

and an armature 14 is pivotally mounted on its inner end. As shown, the armature V14C is disposed to engage'both legs of the core 11.

A magnetizing coil 15 of the device is mounted on lone leg of the core 1l and is disposed to be connected to a source of alternating current (not shown). Upon the connection of the coil 15 to a source of supply, the core 11 becomes energized to attract the armature 14 which seats itself on both ends of the core 11.

l A bimetallic latch 16 is so mounted on the bolts 17 that itis associated with the tail piece 13 of the lever 12. The details of this thermally-responsive latch are disclosed in the copending application of Charles H. Hodgkins, Serial No. 52,267, assigned to Westinghouse Electric & Manufacturing Company, but an understanding of its structure may be had from Fig. 2 of my drawing.

Vassume the position shown in dotted lines,

thereby releasing the -tail piece 13.

A coil 21 of relatively few turns is wound on a projecting arm 22 provided on the core 11. The terminals of the coil 21 are connect; ed to the terminals 18 and 19 of the latch 10. 'l`herefore,.the coil 2l, when energized, provides a source of energy for heating the latch 16. In its open position, the armature 11 rests in Contact with thc projecting arm 22 and, therefore, when the coil 15 is lirst excited, and, when the lever 12 is hitched open, by the latch 16, the path of the flux which has been set up in the core 11 by the energization of the coil 15 must pass through the lever 12, the armature 141. the non-magnetic adjusting screw 23 and tho projecting arm 22 of the core, thereby completing. the magnetic circuit.

It will be seen that, before the closure of the armature 14, the flux will follow the path outlined above, rather than traverse the air gap existing between the core 11 and the armature 14, which path is of considerably higher reluctance than the first. In this way, a transformer action is established between the coil 15 and the coil 21, while the armature remains open. acurrent is induced in the coil 21 and supplied to the latch 16. When the current, induced iu the coil 2l, has been flowing 'for a jecting arm 22 is interrupted and the transformer action between the coils 15 and 21 is no longer existent. Thus, after the armature has assumed its closed position, current is no longer flowing from the coil 21 to the` latch 16 and, since there is no source of energy for heating the latch, the latch willx cool andresume its original shape.

Referring now to Fig. 3, an application of the invention to a system of control for an induction motor 24 is shown. The operating coil 15 of the magnetically operated device is connected across one phase of the supply linev 25 for the motor 24. When the main switches 26 are closed, the coil 15 becomes excited and the core energized. Since the lever 12 is held open by the latch 16, the path of the iux setv up in the core 11 by the excitation of coil 15 will be through the lever 12, the armature 14 and the projecting arm 22, from whence it returns to the core 11. l

When an alternating flux exists in the proj ection 22, a current will be induced in the coil 21, which will be conducted through the conductors 27 to the terminals 2,8 which are connected, one to the terminal 18 and the other to the terminal 19, of the latch 16. Then the current which is induced in the coil 21 iows through the latch 16, heating the' sections 20 and, after a .short period of time, causing the latch to buckle and release the tail piece 13, which will allow the closure of the armature 14. A

Upon the closure of the armature 14, the projecting arm 22 will be eliminated from the magnetic circuit and'no further transformer action between the coils 15 and 21 will occur. Thus, the inductive influence having been removed, no current will flow into the latch 16, and it may return to its normal position.

Vhen the armature 14 is closed, it actuates a contact member 29 and short-circuits the starting resistor 30 for the motor 24. The time delay caused by the thermally-responsive latch 16 constitutes a very desirable featurefor this type of control system, since it is quite necessary that there be an appreciable interval of time between the impression of the line voltage on the motor and short-circuiting of the starting resistor 30. The length of the aforesaid interval of time may be varied in accordance with the operating conditions of lt-he mot-or by varying the cross sectinal area of the sections 20 of latch 16, or by means of thereof, it is to be understood thatthe scope of its application is in no way limited to the embodiment hereinbefore set forth.

.I claim as my invention:

1. In an electromagnetically operated device, a substantially U-shaped corev disposed to provide apath for magnetic flux, a coil for energizing the core connected to an alter'- nating-current source of power,gan,. armature pivotally mounted for movement relative to the core, said armature being' disposed to engage the core and form' a closed magnetic path, a bimetallic latch disposed to retain the armature in its open position, an arm projecting from one side of the core, said arm being disposed to engage the free end of the armature,when in its open position, a secondary coil wound on the projecting arm, said secondary coil being disposed to receive energy through induction from the lirst coil and to supply energy for heating the bimetallic latch, thereby springing said latch after a time interval and allowing the closure of the armature, and means for eliminating the secondary coil from the magnetic path.

2. The combination with an electromagnetically operated device for use in alternating-current circuits, of a secondary coil disposed to have current induced in it by the operating magnetic flux of thedevice when in its open position, means for eliminating said secondary coilfrom the magnetic path when the device is in its closed position, a thermally responsive latch for retaining the device in its open position, andmeans whereby said latch may be actuated by the current supplied'from the secondary coil.

3. A time-element relay comp-rising, 1n combination, a main core member, an armature member disposed to engage the lnan core member to establish a main magnetic circuit, means for moving the armature relative to the core member, an auxiliary core member associated with the main core member, said auxiliary core member, .main core member and armature moving means being disposed to establish a magnetic circuit, and a thermally responsive latch for the armature moving means cooperative to retain the armature spaced from the main core member, coils mounted on said main and auxiliary core members, said coils being inductively associated, the thermally responsive latch being connected to the coil on the auxiliary clore member and responsive to current flowing in the coil on the main core member thereby to release the armature and 4interrupt the inductive action between the coils. e

4. In a time-element relay, main and auxiliaryv coils inductively related, a movable armature for establishing a closed magnetic circuit through the main coil, to interrupt the inductive action between the coils, a thermally responsive latch connected in circuit relation with the auxiliary coil, Asaid latch being operative t0 maintain the movable armature 4tive action between the coils.

In testimony whereof, I have hereunto subscribed my name this 31st day of October,

HENRY D. JAMES. 

